A large number of carbapenem compounds have been prepared and investigated for clinical efficacy. Meropenem, ertapenem, doripenem and biapenem are some of the carbapenem compounds available in the market for treating various bacterial infections. The processes for preparing carbapenem compounds of Formula I and their intermediates are described in several prior art references including U.S. Pat. Nos. 5,424,422; 4,683,296; 4,833,167; 5,104,984; 5,574,152; 5,587,474; 5,260,438; 5,414,081; 6,867,297; 5,792,861; 5,578,722; 5,973,142; 6,080,854; 6,340,751; 6,858,727; 5,231,179; 6,011,150; 5,703,234; 5,580,976; 5,493,018; 5,442,057; 6,162,911; 5,731,431; 4,918,184; and 5,075,437, EP Patent No. 0 300 657131, EP Application No. 0 444 889 A1 and 0 836 607 A1, PCT Publication No. WO 02/020476, Japanese Patent Nos. 2510860; 2592110; 2902178; 3219833; 3388874; 3479720; 3761096; 3080417; and 3467265, Japanese Publication Nos. 07-005590; 63-112558; 02-178262; 04-117382; 04-368365; 04-368386; 06-065195; 2002-338572; 08-081439; 08-325261; 08-311092; 09-031054; 09-316071; 2000-044537; 07-013058; 09-031075; 2000-044587; 2003-026680; 10-077263; 2003-277390; and 2000-007676 A2, Yutaka et al, Org. Process Res. Dev. (2003) 7:846-850, Sunagawa et al., J. Antibiot. (Tokyo), (1990) 43(5):519-532 and Haruki et al., Heterocycles, (1995) 36:145 159 41:147-159.
The carbapenem compounds of Formula I are generally prepared in the prior art by reacting a compound of Formula VIII with a compound of Formula IX
wherein                R1 is C1-3 alkyl        B is —P(O)(OR)2 or —SO2R, wherein R is substituted or unsubstituted C1-6 alkyl, aralkyl or aryl,        P1 is hydrogen or a carboxyl protecting group        P3 is hydrogen or a hydroxyl protecting group, and        A is as defined in Formula I.        
There are several multi-step synthetic routes available in the prior art for preparing the compound of Formula VIII via various azetidinone intermediates. For example, U.S. Pat. No. 4,350,631 provides the following process for the preparation of the compound of Formula VIII.

Similar synthetic routes for preparing the compound of Formula VIII are also described in U.S. Pat. Nos. 4,499,278; 4,360,684; 4,312,871; 4,282,148; 4,273,709; and 4,262,010. However, these processes involve isolation and purification of the intermediates at various steps. Japanese Publication No. 10-087657 provides a two-step process for the preparation of a keto intermediate.

Step-1 of the above process described in Japanese Publication No. 10-087657 is carried out in the presence of imidazole, dimethylaminopyridine and ethyl acetate at 60° C. for 4 h. Step-2 is carried out in the presence of magnesium mono-p-nitrobenzyl malonate and ethyl acetate at 50° C. for 2.3 h. However, Japanese Publication No. 10-087657 does not disclose any method to isolate, purify or cyclize further the keto compound obtained in step-2. Japanese Publication No. 10-087657 also does not disclose any specific method to obtain any carbapenem antibiotic from the disclosed process.